Synthesis of polyoxothiometalates through site-selective post-editing sulfurization of polyoxometalates

Polyoxometalates (POMs) function as platforms for synthesizing structurally well-defined inorganic molecules with diverse structures, metals, compositions, and arrangements. Although post-editing of the oxygen sites of POMs has great potential for development of unprecedented structures, electronic states, properties, and applications, facile methods for site-selective substitution of the oxygen sites with other atoms remain limited. Herein, we report a direct site-selective oxygen–sulfur substitution method that enables transforming POMs [XW12O40]4− (X = Si, Ge) to Keggin-type polyoxothiometalates (POTMs) [XW12O28S12]4− using sulfurizing reagents in an organic solvent. The resulting POTMs retain the original Keggin-type structure, with all 12 surface W 
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Created by potrace 1.16, written by Peter Selinger 2001-2019
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 O groups selectively converted to WS without sulfurization of other oxygen sites. These POTMs show high stability against water and O2 in organic solvents and a drastic change in the electronic states and redox properties. The findings of this study represent a facile method for converting POMs to POTMs, leading to the development of their unique properties and applications in diverse fields, including (photo)catalysis, sensing, optics, electronics, energy conversion, and batteries.


Instrument
Elemental analyses for carbon, hydrogen, nitrogen, and sulfur were performed on a MICRO CORDER JM10, HSU-20, and ICS-1100 at the Open Facility Center, Tokyo Institute of Technology.Ultraviolet-visible absorption spectra were measured using a Shimadzu UV-3600 Plus with a 1 cm quartz cell at room temperature (∼25 °C).IR spectra were measured on a JASCO FT/IR-4100 spectrometer using KBr disks.Raman spectra were measured on a JASCO NRS-5100 spectrometer under an irradiation laser of wavelength λ = 532 nm (0.1 mW).ESI-mass spectra were recorded on a Shimadzu LCMS-9050 instrument and a Waters Xevo G2-XS QTof instrument.Cyclic voltammetry measurements were performed with a BioLogic VSP-300 at the scan rate of 50 mV s −1 .A standard three-electrode arrangement was employed with a glassy carbon disk electrode as the working electrode and a platinum wire as the counter electrode.The potentials were measured using Ag/AgNO3 reference electrode (10 mM AgNO3, 100 mM TBAClO4 in acetonitrile).

X-ray crystallographic analysis
Single-crystal X-ray diffraction measurements were made on BL02B1 beamline at the SPring-8 facility of the Japan Synchrotron Radiation Research Institute (Proposal number; 2023A1731, 2023B1842) with a PILATUS3 X CdTe 1M detector at −173°C.The incident X-ray beam (λ = 0.4132 Å) was monochromatized by a Si(311) double-crystal monochromator.The data collection and process were conducted using RAPID AUTO and CrysAlisPro software S2 , respectively.In the reduction of data, Lorentz, polarization, and empirical absorption corrections were made.The structural analyses were performed using Olex 2 and WinGX.S3,S4 Structures were solved using SHELXT-2018/1 (intrinsic phasing methods) and refined by SHELXL-2018/3.S5,S6 All non-hydrogen atoms (C, O, Si, P, S, and W) were refined anisotropically.CCDC-2322226 contains the supplementary crystallographic data.The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

Bond valence sum (BVS) calculations
The BVS values were calculated by the expression for the variation of the length rij of a bond between two atoms i and j in observed crystal with valence Vi.
where B is constant equal to 0.37 Å, r'0 is bond valence parameter for a given atom pair. S7 performed using Gaussian 16, Rev. B.01.The geometries used in the calculation were based on the crystal structures determined in this study.The anion structures of ISi and IISi were optimized at the CAM-B3LYP functional with 6-31G(d) for Si, O and S, and LanL2DZ for W by using the polarizable continuum model with the parameters of the integral equation formalism model for acetonitrile.S4

Fig. S4
Fig. S4 Crystal packing of the TPP salt of IISi viewing from (a) c-axis direction and (b) a-axis direction.

Fig. S8
Fig. S8 Energy diagram and molecular orbitals of IISi based on the DFT study.

Table S1 .
Crystallographic parameters of the TPP salt of IISi.

Table S2 .
BVS values for S atoms of the TPP salt of IISi.

Table S3 .
BVS values for Si and W atoms of the TPP salt of IISi.